Multi-planar adjustable connector

ABSTRACT

A connection assembly between a spinal implant rod and a vertebral anchor. The assembly has a split ring, a clamp, a collet and optionally a nut. The split ring is located inside the clamp and the collet is inserted through each of the clamp&#39;s arms. In use, the spinal implant rod is placed inside the split ring and the shaft or shank of the vertebral anchor is placed inside the collet. Drawing the arms of the clamp together then tightens the connection assembly, which closes the collet around the vertebral anchor and closes the split ring around the implant rod. Threading a nut on one end of the collet or directly threading the collet into one of the arms of the clamp tightens the assembly.

This invention relates to a laterally adjustable connection between aspinal rod and a vertebral anchor, and more particularly relates to aspinal implant connection that is dorsally adjustable.

BACKGROUND OF THE INVENTION

Spinal implant systems provide a rod for supporting the spine and forproperly positioning components of the spine for various treatmentpurposes. Bolts, screws, and hooks are typically secured to thevertebrae for connection to the supporting rod. These vertebral anchorsmust frequently be positioned at various angles due the anatomicalstructure of the patient, the physiological problem being treated, andthe preference of the physician. It is difficult to provide secureconnections between the spinal support rod and these vertebral anchorsat all the various angles and elevations that are required, especiallywhere there are different distances between the rod and bolts and wherethese components are located at different heights on the patient.

One solution to this problem is shown in U.S. Pat. No. 5,938,663 toPetreto, the disclosure of which is specifically incorporated into thisspecification by reference. This patent describes a connection between arod and a vertebral anchor, through which a surgeon may vary the anglebetween a spinal rod and the anchor to which the rod is attached. Theconnection is equipped with a ball joint that allows the surgeon to fixthe desired angle between the anchor and the rod. This system, however,has no elevation adjustment capability after the bone anchor isinstalled because the clamp in that invention must be secured between anut and an immovable shoulder on the bone anchor.

What is needed is a connection assembly between a spinal rod and avertebral anchor that allows the surgeon to fix the desired elevationbetween a rod and the bone anchor as well as fix the desired anglebetween the anchor and rod. The following invention is one solution tothat need.

SUMMARY OF THE INVENTION

In one aspect, this invention is a connection assembly between a spinalimplant rod and a vertebral anchor. The connection assembly has acompressible ring to receive a portion of the spinal implant rod. Theconnection assembly also has a clamp to hold the compressible ring, andthe clamp has two arms with a coaxial channel in each arm. Theconnection assembly also has a collet that is positioned inside thechannels to hold the shaft of the vertebral anchor. A nut is thenthreadably engaged to the end of the collet extending from the clamp totighten the connection assembly to the anchor and rod.

In another aspect, this invention is a connection assembly between aspinal implant rod and a vertebral anchor. The connection assembly has acompressible ring to receive a portion of the spinal implant rod. Theconnection assembly also has a clamp to hold the compressible ring, andthe clamp has two arms with a coaxial channel in each arm. Theconnection assembly also has a collet that is positioned inside thechannels to hold the shaft of the vertebral anchor. The collet is thenthreadably engaged to one of the arms of the clamp to tighten theconnection assembly to the anchor and rod.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the invention.

FIG. 2 is an elevational cross-sectional view of one embodiment of theinvention.

FIG. 3 is a perspective view of a compressible ring usable in oneembodiment of the invention.

FIG. 4 is a perspective view of a clamp usable in one embodiment of theinvention.

FIG. 5 is a perspective view of a collet usable in one embodiment of theinvention.

FIG. 6 is an elevational cross-sectional view of one alternativeembodiment of the invention.

FIG. 7 is an end cross-sectional view of a clamp usable in oneembodiment of the invention.

FIG. 8 is an end cross-sectional view of a clamp usable in onealternative embodiment of the invention.

FIG. 9 is a perspective view of a compressible ring usable in onealternative embodiment of the invention.

FIG. 10 is a perspective view the invention installed in a portion ofthe human spine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Specific language is used in the following description to publiclydisclose the invention and to convey its principles to others. No limitson the breadth of the patent rights based simply on using specificlanguage are intended. Also included are any alterations andmodifications to the description that should normally occur to one ofaverage skill in this technology.

A connection assembly 1 according to one embodiment of the invention isshown in FIGS. 1 and 2. Connection assembly 1 includes a compressiblering or split ring 3, a shackle or clamp 4, a collet 5, and a nut 6.Compressible ring 3 has an aperture 2 for receiving a rod “A” in aspinal implant system and collet 5 has a socket 7 for receiving theshank or post 8 of a vertebral anchor “B”. As shown, socket 7 ispreferably open between the top and bottom of the connection assembly toallow post or shank 8 to extend through collet 5 so that collet 5 can belocked into place anywhere along the length of shank 8.

Referring to FIG. 4, shackle or clamp 4 has lower and upper branches (orarms) 9 and 10 and a head 11 that links these branches. The externalfaces 12 and 13 of branches 9 and 10 are preferably substantially flat;however, other surfaces are also contemplated. For example, the externalface 12 of branch 9 may be countersunk for collet 5, or the externalface 13 of branch 10 may be concave to accept a complementary convexsurface on nut 6. Be that as it may, branches 9 and 10 have coaxiallyaligned channels 14 and 15 of appropriate diameter and contour to acceptcollet 5 inside clamp 4.

Referring to FIG. 5, collet 5 is generally a cylindrical member having afirst end 16 with multiple fingers 17, a threaded second end 18, and atapered portion 19 between ends 16 and 18. Threaded second end 18generally has a constant diameter that is readily accepted into channels14 and 15 of clamp 4. The tapered portion 19 is flared in a fashion thatwidens over the length of collet 5, that is, widening as one moves froma position 22 on the interior surface of collet 5 and toward end 16. Andthough collet 5 is shown with a straight taper, it is also contemplatedthat the taper could be convex as well as concave over tapered portion19. Regardless of the shape, channel 14 in clamp 4 (FIG. 2) contains agenerally complementary profile to mate against whatever profile taperedportion 19 may have. That is, complementary in a manner that when collet5 is forced into channel 14 beyond a position of mere contact againstclamp 4, channel 14 will deflect fingers 17 inward toward the axis 23 ofsocket 7. Fingers 17 can be formed in most any fashion on collet 5.Preferably, however, they are integral and are formed in tapered portion19 by placing a plurality of slots 21 that open between socket 7 and theexterior surface of collet 5 in the sides of collet 5.

Clamp 4 defines an interior cavity 24, which is preferably open on bothsides of the clamp. Interior cavity 24 has a generally arched sidewall25 (FIG. 7) that provides a concave surface to accept the generallysperical or convex exterior of compressible ring 3. Alternatively,interior cavity 24 could also include coaxial shoulders or arches 26inside cavity 24. (FIG. 8) These shoulders 24 provide an edge 27 to gripcompressible ring 3 when clamp 4 is later tightened.

Referring to FIG. 3, compressible ring 3 has a preferablystraight-through aperture 2 that is sized to receive spinal implant rod“A”. The external face 28 of compressible ring 3 has a preferablygenerally spherical profile that is complementary to the interiorprofile of interior cavity 24 in clamp 4. As shown, ring 3 has a slot 30that opens between the exterior 28 and aperture 2. Optionally, ring 3may also have a groove 31 (FIG. 9) to further increase the ease withwhich the user may compress split ring 3. Moreover, ring 3 may alsoinclude a chamfer 29 around one or both sides of aperture 2 to assistthe user in inserting the spinal implant rod “A” into connectionassembly 1.

Referring back to FIGS. 1 and 2, screwing nut 6 onto the threaded secondend 18 of collet 5 clamps the upper branch 10 and the lower branch 11 ofclamp 4 together. This action, in turn, compresses split ring 3 thatresides inside cavity 24 around spinal implant rod “A” and deflectsfingers 17 of collet 3 around vertebral anchor “B”. Compressing splitring 3 tightens assembly 1 to implant rod “A” and deflecting fingers 17tightens assembly 1 to vertebral anchor “B”. Optionally, the user mayenhance this connection by roughening the surface of vertebral anchor“B”, roughening the surface of implant rod “A”, roughening the externalface 28 of ring 3, or roughening the surface of interior cavity 24 ofclamp 4.

A variant of assembly 1 is shown in FIG. 6. In this embodiment, collet 3is inverted and threads into the lower branch 9 of clamp 4. The insideof channel 15 in the upper branch 10 is then complementary tapered orprofiled (as previously described in regard to channel 14) to accept thetapered portion 19 of collet 5. The collet is then rotated in thisembodiment by a tool (not shown) that grips collet 5 by depressions orslots 32 in end 16. Turning collet 3 into the now threaded channel 14clamps the upper branch 10 and the lower branch 11 of clamp 4 together.As with the previous embodiment, this action compresses split ring 3around spinal implant rod “A” and deflects fingers 17 of collet 3 aroundvertebral anchor “B”. Compressing split ring 3 tightens assembly 1 toimplant rod “A” and deflecting fingers 17 tightens assembly 1 tovertebral anchor “B”.

An installation of the connection assembly 1 is shown in FIG. 10. Ingeneral, the surgeon places the vertebral anchors into the pedicle ofeach vertebra. With the screws in place, a rod “A” is chosen having thedesired rigidity, which is then bent to the necessary contour. Theconnection assemblies 1 are loaded onto the rod. Then the connectors 1are sequentially lowered over the shanks of the vertebral anchors. Onceplaced at the desired elevation on each shank, the connection assemblies1 are then tightened to secure the rod to the anchor by tightening nut 6(FIGS. 1 and 2) or collet 5 (FIG. 6) depending on which embodiment ofthe invention is being used. Optionally, the surgeon may also place theconnections on the anchors and then feed the rod through the connectors.

While the invention has been illustrated and described in detail, thisis to be considered illustrative and not restrictive of the patentrights. The reader should understand that only the preferred embodimentshave been presented and all changes and modifications that come withinthe spirit of the invention are included if the following claims or thelegal equivalent of these claims describes them.

1-20. (cancelled)
 21. A spinal implant system comprising: a vertebralanchor having a shank with a first unthreaded portion; a spinal implantrod having a second unthreaded portion; a compressible ring, saidcompressible ring defining an aperture to receive the unthreaded portionof said spinal implant rod; a clamp, said clamp having first and secondarms, said first arm having a fist channel and said second arm having asecond channel,; and a collet, said collet positioned inside the firstand second channels of said clamp, said collet defining a socket to holdthe unthreaded portion of said vertebral anchor, wherein said collet isadjustably anchorable among a plurality of positions along the length ofthe first unthreaded portion of said anchor, and said ring is adjustablyanchorable among a plurality of positions along the length of the seconduntheaded portion of said rod.
 22. The connection assembly of claim 21wherein said collet has a threaded end, and which further comprises anut, said nut threadably engaged to the threadedend of said collet. 23.The connection assembly of claim 21, wherein one said channel of saidclamp has a straight internal taper in at least a portion of said onechannel.
 24. The connection assembly of claim 23, wherein a portion ofsaid collet has a straight outside taper and the inside taper of thesecond arm of said clamp is complementary shaped to the taper of saidcollet.
 25. The connection assembly of claim 21, wherein saidcompressible ring has at least a partially spherical exterior and thechannel of said clamp has a substantially mating concave surface. 26.The connection assembly of claim 21, wherein the collet has three ormore slots near the second end of said collet.
 27. The connectionassembly of claim 21, wherein at least one channel of said clamp has asidewall and wherein at least a portion of the sidewall includes atleast one edge to bear against the outside of said compressible ring.28. The connection assembly of claim 21, wherein said compressible ringis split.
 29. The connection assembly of claim 28, wherein saidcompressible ring has an exterior surface and wherein said compressiblering also includes a groove in the exterior surface.
 30. The connectionassembly of claim 21, wherein said collet has an end and at least oneslot near the end, and wherein said compressible ring is split.